Date of Graduation

12-2023

Document Type

Thesis

Degree Name

Master of Science in Horticulture (MS)

Degree Level

Graduate

Department

Horticulture

Advisor/Mentor

Cato, Aaron

Committee Member

McWhirt, Amanda L.

Second Committee Member

Joshi, Neelendra K.

Keywords

Broad Mite (Polyphagotarsonemus latus); Cultural Control; Floricane-fruiting Blackberries; Integrated Pest Management (IPM); Optimal Sampling

Abstract

Broad mite, (Polyphagotarsonemus latus Banks) (Acari: Tarsonemidae), is an economically important pest of blackberry production across the world. Since it was first reported on primocane-fruiting blackberries in 2010, little work has gone into developing IPM tools and understanding impact on floricane-fruiting cultivars. The objective of this thesis was to evaluate the effect of broad mite feeding on floricane-fruiting cultivars of blackberry, develop an efficient and accurate field scouting strategy, and investigate the impact of cultivar and trellising technique on the development of broad mite populations. Experiments consisted of evaluating floricane fruiting cultivars by quantifying broad mite populations and cataloging their damage. Next, analysis of optimal sampling strategies were conducted within established commercially produced blackberries. Finally, broad mite infestation of various blackberry cultivars and trellis systems was explored for potential avenues of cultural control. These studies suggest that broad mite feeding on blackberry primocanes at low-moderate population densities does not affect floricane yield or the timing of bud break, number of blossoms produced, or floral development. Our data suggests that scouting based on visual injury is significantly more time efficient than leaflet sampling, and adequate estimates of broad mite density can be made with visual assessments alone. In addition, blackberry cultivars with higher levels of trichome density were observed to have decreased broad mite densities, and blackberries grown using the T-trellis system exhibited higher densities of broad mite than those grown using the RCA trellis system. These results together provide multiple facets necessary for an improved IPM framework necessary to sustainably manage broad mite. Our results suggest that multiple forms of cultural control may exist for broad mite, and we were able to establish an accurate and time efficient field sampling strategy. Future work should be focused on assessing higher densities of broad mite to further understand their impact on floricane fruiting cultivars.

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